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An easy, safe, simple, and efficient pH‐switchable hydrophobic deep eutectic solvent (DES)‐based liquid‐phase microextraction was developed for the extraction of chlorobenzenes (CBs) from water samples followed by a gas chromatography–electron capture detector (GC–ECD). The switchability of the synthesized DESs was tested by changing the pH. The DES synthesized from thymol:octanoic acid (OA) in a molar ratio of 2:1 had the highest efficiency in extracting CBs from water samples. 1,4‐Dibromobenzene was used as internal standard (IS). The optimal conditions were established to be 20.0 µL of thymol:OA (2:1), 100 µL of 5 mol L−1 KOH, 100 µL of 5 mol L−1 HCl, 60 s of extraction time, and without salt addition. Under the optimum conditions, the calibration graphs were linear in the range of 0.005–150 µg L−1, and limits of detection were in the range of 0.001–0.03 µg L−1. The relative standard deviations, including intraday and inter‐day for 5.0 µg L−1 of dichlorobenzene isomers, 2.0 µg L−1 of trichlorobenzene and tetrachlorobenzene isomers, and 0.50 µg L−1 of pentachlorobenzene and hexachlorobenzene isomers in water with using IS, were in the range of 0.6%–3.2% (n = 7) and 3.8%–6.7% (n = 7), respectively. The accuracies, including inter‐day and intraday, were in the range of 93.5%–106.3% and 91.7%–109.4%, respectively. [ABSTRACT FROM AUTHOR]

In the present research, a novel hydrophobic deep eutectic solvent‐based dispersive liquid‐liquid microextraction technique was established and combined with high‐performance liquid chromatography‐ultraviolet for the determination of triazine herbicides in fruit and vegetable samples. A deep eutectic solvent was synthesized using l‐menthol as a hydrogen bond acceptor and ethylene glycol as a hydrogen bond donor and used as a green extractant. The characterization of deep eutectic solvent was investigated by Fourier‐transform infrared, nuclear magnetic resonance, and thermogravimetric analysis. Under the optimum conditions, relative standard deviation values for intra‐day and inter‐day of the method based on seven replicate measurements of 50.0 μg/kg of triazines were in the range of 2.8%–5.5% and 3.7%–7.2%, respectively. The calibration graphs were linear in the range of 3.0–500 μg/kg and the limits of detection were in the range of 1.0–2.0 μg/kg. The relative recoveries of different fruit and vegetable samples that have been spiked with two levels of target compounds were 91.5%–109.8%. The method has good linearity, sensitivity, accuracy, and precision. It is also environmentally friendly and was successfully used to determine the concentrations of triazines in fruit and vegetable samples. [ABSTRACT FROM AUTHOR]

BACKGROUND: In this research, a new extraction method based on dispersive liquid–liquid microextraction and the solidification of deep eutectic solvent has been developed for the determination of heavy metals in soil and vegetables prior to their analysis by graphite furnace atomic absorption spectrometry (GFAAS). In this method, a green solvent consisting of 1‐decyl‐3‐methylimidazolium chloride and 1‐undecanol was used as an extraction solvent, yielding the advantages of material stability, low density and a suitable freezing point near room temperature. RESULTS: Under optimal conditions, enrichment factors are in the range of 114–172. The calibration graphs are linear in the range of 0.02–200 µg kg−1 and limits of detection are in the range of 0.01–0.03 µg kg−1. Repeatability and reproducibility of the method based on seven replicate measurements of 0.80 µg kg−1 of Hg and 0.20 µg kg−1 of Pb and Cd in analyzed samples were in the range of 2.3–4.1% and 3.7–6.6%, respectively. CONCLUSION: A new deep eutectic solvent consists of two parts: 1‐decyl‐3‐methylimidazolium chloride and 1‐undecanol in a molar ratio of 1:2. The accuracy of the proposed procedure was also assessed by determining the concentration of the studied metal ions in a polluted farmland soil standard reference material. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Persistent sample circulation microextraction (PSCME) combined with graphite furnace atomic absorption spectrometry (GFAAS) was developed as a high pre‐concentration technique for the determination of heavy metals in fish species. In this method, a few microliters of organic solvent (40.0 µL carbon tetrachloride) was transferred to the bottom of a conical sample cup. Then 10.0 mL of aqueous solution was transformed to fine droplets while passing through the organic solvent. At this stage, metal–ligand hydrophobic complex was extracted into the organic solvent. After extraction, 20 µL of extraction solvent was injected into the graphite tube using an auto‐sampler. RESULTS: Under optimal conditions, enrichment factors and enhancement factor were in the range of 180–240 and 155–214, respectively. The calibration curves were linear in the range of 0.03–200 µg kg–1 and the limits of detection (LODs) were in the range of 0.01–0.05 µg kg–1. Repeatability (intra‐day) and reproducibility (inter‐day) for 0.50 µg L–1 Hg and 0.10 µg L–1 Cd and Pb were in the range of 3.1–4.2% (n = 7) and 4.3–6.1% (n = 7), respectively. CONCLUSION: Potential human health risk assessment was conducted by calculating estimated weekly intake (EWI) of the metals from eating fish and comparison of these values with provisional tolerable weekly intake (PTWI) values. EWI data for the studied metals through fish consumption were lower than the PTWI values. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Dispersive liquid-liquid microextraction based on solidification of floating organic droplet was developed for the extraction of methadone and determination by high-performance liquid chromatography with UV detection. In this method, no microsyringe or fiber is required to support the organic microdrop due to the usage of an organic solvent with a low density and appropriate melting point. Furthermore, the extractant droplet can be collected easily by solidifying it at low temperature. 1-Undecanol and methanol were chosen as extraction and disperser solvents, respectively. Parameters that influence extraction efficiency, i.e. volumes of extracting and dispersing solvents, pH, and salt effect, were optimized by using response surface methodology. Under optimal conditions, enrichment factor for methadone was 134 and 160 in serum and urine samples, respectively. The limit of detection was 3.34 ng/mmL in serum and 1.67 ng/mL in urine samples. Compared with the traditional dispersive liquid-liquid microextraction, the proposed method obtained lower limit of detection. Moreover, the solidification of floating organic solvent facilitated the phase transfer. And most importantly, it avoided using high-density and toxic solvents of traditional dispersive liquid-liquid microextraction method. The proposed method was successfully applied to the determination of methadone in serum and urine samples of an addicted individual under methadone therapy. [ABSTRACT FROM AUTHOR]

An ultrasound-assisted dispersive liquid–liquid microextraction based on solidification of a floating organic drop method followed by high-performance liquid chromatography was developed for the extraction, preconcentration, and determination of trace amounts of organophosphorus pesticides in rice samples. Variables affecting the performance of both steps were thoroughly investigated. Some effective parameters on extraction were studied and optimized. Under the optimum conditions, recoveries for rice sample are in the range of 58.0–66.0%. The calibration graphs are linear in the range of 4–800 µg/kg and, limits of detection and limits of quantification are in the range of 1.5–3 and 4.2–8.5 µg/kg, respectively. The relative standard deviation for 50.0 µg/kg of organophosphorus pesticides in rice sample are in the range of 4.4–5.1% (n = 5). The obtained results show that proposed method is a fast and simple method for the determination of pesticides in cereals. [ABSTRACT FROM AUTHOR]

A novel and sensitive dispersive liquid-liquid microextraction method based on the solidification of the floating organic drop combined with high-performance liquid chromatography and ultraviolet detection was used for the determination of atorvastatine in blood serum samples. The chromatographic separation of atorvastatin was carried out using methanol as the mobile phase organic modifier. Various parameters affecting the extraction efficiency were optimized, such as the kind and volume of extraction solvent (1-undecanol) and disperser solvent (acetonitrile), pH, and the extraction time. The calibration curve was linear in the range of 0.2-6000 μg/L of atorvastatin ( r2 = 0.995) with a limit of detection of 0.07 μg/L. The relative standard deviation for 100 μg/L of atorvastatin in human plasma was 8.4% ( n = 4). The recoveries of plasma samples spiked with atorvastatin were in the range of 98.8-113.8%. The obtained results showed that the proposed method is fast, simple, and reliable for the determination of very low concentrations of atorvastatin in human plasma samples. [ABSTRACT FROM AUTHOR]

A new pretreatment method, SPE combined with dispersive liquid-liquid microextraction, was proposed for the determination of abamectin in citrus fruit samples for the first time. In this method, fruit samples were extracted by ultrasound-assisted extraction followed by SPE. Then, the SPE was used as a disperser solvent in the next dispersive liquid-liquid microextraction step for further purification and enrichment of abamectin. The effects of various parameters on the extraction efficiency of the proposed method were investigated and optimized. Good linearity of abamectin was obtained from 0.005 to 10.0 mg/kg for B1a and from 0.05 to 10.0 mg/kg for B1b with correlation coefficient ( r2) of 0.998 for B1a and 0.991 for B1b, respectively. The LODs were 0.001 and 0.008 mg/kg (S/N = 3) for B1a and B1b, respectively. The relative recoveries at three spiked levels were ranged from 87 to 96% with the RSD less than 11% ( n = 3). The method has been successfully applied to the determination of abamectin in citrus fruit samples. [ABSTRACT FROM AUTHOR]

Dispersive liquid-liquid microextraction based on solidification of floating organic drop coupled with HPLC- UV detection as a fast and inexpensive technique was applied to the simultaneous extraction and determination of traces of two common herbicides, alachlor and atrazine, in aqueous samples. The critical experimental parameters, including type of the extraction and disperser solvents as well as their volumes, sample pH, salt addition, and extraction time were investigated and optimized. Under the optimum conditions, the calibration graphs found to be linear in the range of 0.1-200 μg/L with LOD in the range of 0.02-0.05 μg/L. The RSDs were in the range of 4.2-5.3% ( n = 5). The relative recoveries of well, tap, and river water samples which have been spiked with different levels of herbicides were 94.0-106.0, 99.0-105.0, and 88.5-97.0%, respectively. [ABSTRACT FROM AUTHOR]

Dispersive liquid-liquid microextraction coupled with high-performance liquid chromatography-ultraviolet detection as a fast and inexpensive technique was applied to the simultaneous extraction and determination of traces of three common herbicides, 2,4- D, alachlor and atrazine, in aqueous samples. The critical experimental parameters, including type of the extraction and disperser solvents as well as their volumes, sample p H, salt addition, extraction time and centrifuging time, and speed were investigated and optimized. Under the optimum conditions, the calibration graphs found to be linear in the range of 0.3-200 μg/L with limits of detection in the range of 0.05-0.1 μg/L. The relative standard deviations were in the range of 4.5-6.2% ( n = 7). The relative recoveries of well, tap, and river water samples which have been spiked with different levels of herbicides were 92.0-107.0, 82.0-104.0, and 82.0-86.0%, respectively. [ABSTRACT FROM AUTHOR]